A data-driven model for valve stiction

The presence of nonlinearities, e.g., striction, hysteresis and backlash in a control valve limits the control loop performance. Striction is the most common problem in spring-diaphragm type valves, which are widely used in the process industry. Though there have been many attempts (EnTech, 1998; Gerry and Ruel, 2001; Horch and Isaksson, 1998; Taha et al., 1996; Piipponen, 1996; McMillan, 1995) to understand the stiction phenomena and model it, there is a lack of a proper model which can be understood and related directly to the practical situation as observed in a real valve in the process industry. This study focuses on the understanding, from real life data, of the mechanism that causes stiction and proposes a new data-driven model of stiction, which can be directly related to real valves. It compares simulation results generated using the proposed model with industrial data

Alpha-canonical form representation of the open loop dynamics of the Space Shuttle main engine

A parameter and structure estimation technique for multivariable systems is used to obtain a state space representation of open loop dynamics of the space shuttle main engine in alpha-canonical form. The parameterization being used is both minimal and unique. The simplified linear model may be used for fault detection studies and control system design and development

Design and development experience with a digital fly-by-wire control system in an F-8C airplane

To assess the feasibility of a digital fly-by-wire system, the mechanical flight control system of an F-8C airplane was replaced with a digital system and an analog backup system. The Apollo computer was used as the heart of the primary system. This paper discusses the experience gained during the design and development of the system and relates it to active control systems that are anticipated for future civil transport applications

Process control performance evaluation in the case of variable set-point with experimental applications

The purpose of this paper is to contribute with some refinements to recent methods of analysis of control loop performance, based on the well-established principle of Internal Model Control (IMC). Lower limits for the absolute value of the integral of control error (IAE) and the total variation of control action (TV) are assumed as reference values for a control considered good or at least acceptable. The overall performance index assumes as a benchmark a controller tuned according to rules of S(implified)IMC technique and is appropriately defined with respect to the lower limits of the two metrics IAE and TV. This allows the assessment of control loop performance, that is, the validity of tuning for PID-type controllers in response to different types of reference change. In fact, one can assess performance in the case of set-point changes as steps, ramps, or generic varying trends over time. In order to demonstrate the validity of the refined technique, several examples of simulation, case studies on a pilot plant, and real industrial data are presented

Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transport project: Current and advanced act control system definition study. Volume 2: Appendices

The current status of the Active Controls Technology (ACT) for the advanced subsonic transport project is investigated through analysis of the systems technical data. Control systems technologies under examination include computerized reliability analysis, pitch axis fly by wire actuator, flaperon actuation system design trade study, control law synthesis and analysis, flutter mode control and gust load alleviation analysis, and implementation of alternative ACT systems. Extensive analysis of the computer techniques involved in each system is included